Method of preparing tetramethyllead

ABSTRACT

A METHOD OF PREPARING TETRAMETHYLLEAD UTILIZING A NOVEL CATALYST CONSISTING OF METHANOL AND DIGLYME WITH OR WITHOUT ANTHRACENE IS DESCRIBED. THE CATALYST IS USED IN QUANTITIES OF AT LEAST 0.02 MOLE OF METHANOL AND DIGLYME PER MOLE OF SODIUM-LEAD ALLOY EMPLOYED. CATALYST COMPOSITIONS, ONE COMPRISING 14 TO 20 WEIGHT PERCENT METHANOL, 58 TO 79.9 PERCENT DIGLYME AND 0.1 TO 28 PERCENT ANTHRACENE AND A SECOND ONE COMPRISING 30 TO 10 PERCENT METHANOL AND 79 TO 90 PERCENT DIGLYME BASIS THE MIXTURE, ARE CLAIMED.

United States Patent 3,642,849 METHOD OF PREPARING TETRAMETHYLLEAD Edward G. Newyear, Corpus Christi, Tex., assiguor to PPG Industries, Inc., Pittsburgh, Pa. No Drawing. Filed Mar. 25, 1970, Ser. No. 22,693 Int. Cl. (307E 7/24 US. Cl. 260437 R 13 Claims ABSTRACT OF THE DISCLOSURE A method of preparing tetramethyllead utilizing a novel catalyst consisting of methanol and diglyme with or without anthracene is described. The catalyst is used in quantities of at least 0.02 mole of methanol and diglyme per mole of sodium-lead alloy employed. Catalyst compositions, one comprising 14 to weight percent methanol, 58 to 79.9 percent diglyme and 0.1 to 28 percent anthracene and a second one comprising 30 to 10 percent methanol and 79 to 90 percent diglyme basis the mixture, are claimed.

BACKGROUND OF THE INVENTION Gasoline formulations have in recent years often included significant quantities of tetramethyllead as an antiknock agent. Tetramethyllead, unlike tetraethyllead, is produced from methyl halide and sodium-lead alloy only with considerable difiiculty and normally requires the presence of a catalyst in the reaction zone. Thus, U.S. Pats. such as US. Pats. 3,048,610; 3,192,420 and 3,401,- 188 and British Pat. 1,015,268 all describe various processes for the manufacture of tetramethyllead from sodium-lead alloy and methyl halide utilizing various catalyst systems.

While the catalyst systems described in the prior art are efiicacious in the production of tetramethyllead in satisfactory quantities, drawbacks are encountered in the utilization of most of them. Thus, various aluminum containing catalysts described in the prior art are found to be somewhat difficult to handle in that they are subject to spontaneous ignition. The utilization of other catalysts such as ammonia in the presence of small quantities of monohydroxylic compounds, as described in the aforementioned British patent, requires sophisticated equipment in order to avoid leaks during reaction. Therefore, while tetramethyllead is capable of being produced in accordance with the various catalyst systems described in the prior art, some of the disadvantages inherent in these prior art catalyst systems are not easily overcome.

THE PRESENT INVENTION In accordance with the present invention a catalyst system which is safe, easy to handle and which requires no special equipment other than that conventionally employed in present commercial plants for the production of tetramethyllead is utilized to manufacture tetramethyllead from methyl halide and sodium-lead alloy in satisfactory yields. Thus, in accordance with the present invention, sodium-lead alloy and methyl halide, preferably as methyl chloride, are reacted in a pressure vessel in the presence of a catalyst comprising methanol and diglyme in quantities of at least 0.020 mole of catalyst per mole of sodiumlead alloy present in the reactor.

In a further embodiment of the instant invention a catalyst system comprising \methanol, diglyme and anthracene is employed to produce tetramethyllead from methyl halide and sodium-lead alloy. The anthracene in this system is present in a quantity of between about 0.15 and about 1.6 percent by weight of the mixture. The preferred embodiment of the latter catalyst system consists essen- 3,642,849 Patented Feb. 15, 1972 tially of diglyme (0.3 to 3.3 percent), methanol (0.07 to 0.8 percent) and anthracene (0.15 to 1.6 percent).

In carrying out the instant invention, recourse to the utilization of conventional autoclaves now employed in the tetramethyllead industry may be had. Thus, autoclaves capable of withstanding pressures of to 600 p.s.i.g. or more are typically employed.

Temperatures at which the reaction may be carried out may 'vary. .In general, reaction temperatures are from -20 C. to 150 C. Preferably the temperatures utilized are in the range of 60 to 130 C.

The methyl halide, utilized as a methylating agent in accordance with the instant invention, is typically methyl chloride; however, the use of other methyl halides is contemplated. The quantity of methylating agent employed normally ranges between 1 mole to 10 moles of methyl halide per mole of sodium-lead alloy used. Preferably, from about 1 to about 4 to about 8 moles or methyl halide per mole of sodium-lead alloy is used.

Sodium-lead alloy utilized in the instant process is typically a lmonosodium-lead alloy containing 50 mole percent sodium and 50 mole percent lead. While a monosodium-lead alloy is preferred in the operation of the instant invention, recourse to sodium-lead alloys having varying molar ratios of sodium to lead may be utilized.

Monosodium-lead alloy as typically used is screened to a inch to 40 mesh size, though any conventional sodium-lead alloy particle size \may be used if desired.

When ternary mixtures are used for catalyst in the instant invention there is present in the' final mixture at least 0.026 mole of diglyme and methanol per mole of the alloy. The anthracene in such instance is utilized in smaller quantities, typically between 0.001 to 0.1 mole per mole of lead alloy. Preferably anthracene when employed in the catalyst, is used in quantities ranging between 0.005 to 0.05 mole.

The novel catalyst compositions of the instant invention include anthracene, diglyme and methanol containing on a weight basis, 0.15 to 1.6 weight percent anthracene, 0.3 to 3.3 weight percent diglyme and 0.07 to 0.8 weight percent methanol basis the alloy fed in the reaction. The novel catalyst compositions contemplated also include diglyme and methanol containing on a weight basis 0.3 to 3.3 weight percent diglyme and 0.07 to 0.8 weight percent methanol basis the alloy fed in the reaction.

In utilizing diglyme and methanol catalyst compositions without any anthracene present to produce tetramethyllead from sodium-lead alloy and methyl halide, the quantities of diglyme and methanol employed are generally in the range of between 0.01 mole of diglyme to 0.2 mole of diglyme per mole of sodium-lead alloy and between 0.01 mole of methanol to 0.2 mole of methanol per mole of sodium-lead alloy. In general the combination of diglyme and methanol is utilized in quantities of at least about 0.2 mole per mole of sodium-lead alloy and preferably, between 0.3 to 0.5 mole per mole of sodium-lead alloy employed. The compositions of diglyme, methanol and anthracene typically contain 14 to 20 percent by weight methanol, 58 to 79.9 percent by weight diglyme and 28 to 0.1 percent by weight anthracene basis the mixture.

For a more complete understanding of the instant invention, reference is made to the following examples:

EXAMPLE I A series of experiments were run utilizing anthracene, diglyme and methanol in a reaction system containing 0.2 mole of sodium-lead alloy and different quantities of methyl chloride. These runs were made in a stainless steel laboratory autoclave at a reaction temperature of :3 C. and with a total reaction time of 2 hours. During the course of the experiment, several runs were made in which the quantities of diglyme, anthracene and methanol were varied considerably. Table 1 shows the composition of the catalyst for 11 experiments conducted to proas Well as the catalyst system methanol and diglyme. The runs were made at a reaction time of 2 hours and at a temperature of 120 C.:4 C. Tetramethyllead yields of these runs on the basis of the sodium charged are shown 5 below in Table 3:

TAB LE 3 Percent TML yield (based on Mole per mole of N aPb Na charged),

Percent experimental by- Methyl Anthrasodium Run No. chloride cene Methanol Diglymo reacted (1.0. EDTA 1 7.70 0. 044 0.13 0.15 77 54 46 6. 09055 0. 16 0.0 36 5 5 7. 90 0.044 0.0 0.12 4 Trace 1 6. 50 0.055 0.14 0. 12 75 41 42 6. 80 0. 044 0.13 0.15 75 41 40 6.40 0.0 0. 15 0.15 72 37 6. 85 0. 0 O. 16 0. 15 82 46 46 7. 35 0. 050 0. 11 0. 14 93 43 6. 70 0.050 0.05 0.15 52 34 34 7. 25 0.0 0.16 0.15 76 44 1 Analysis by gas chromatograph. 2 Analysis by ethylenediaminetetraacetic acid titration.

duce tetramethyllead utilizing this novel catalyst system and the results obtained.

TABLE 1 As will be readily appreciated from the above runs, the catalyst system anthracene, methanol and diglyme is Methyl Catalyst composition, moles Percent Tetrachloride, per mole of alloy methyllead bymoles perf m es 0 Run No. Anthraceue Diglyme Methanol Reacted G .C. EDTA 1 alloy 1 Analysis by gas chromatograph. 1 Analysis by ethylenediaminetetraacetic acid titration.

EXAMPLE II A further set of experiments were undertaken in the same laboratory stainless steel autoclave to produce tetramethyllead using diglyme-methanol with and without anthracene catalyst with methyl chloride and sodium-lead alloy. A reaction temperature of C.:3 C. was employed in these runs and a reaction time of 2 hours was also used in all runs. 0.2 mole of sodium-lead alloy was employed in the reaction mass with varying quantities of methyl chloride. The concentration of the catalyst materials utilized, the methyl chloride concentration in the reaction, the percent sodium reacted, and the tetramethyllead yield obtained during the runs are shown below in Table 2.

TABLE 2 an effective catalyst system for the production of tetramethyllead. It is also readily seen from the above examples that when diglyme and methanol are utilized in the range stated hereinbefore, an effective tetramethyllead reaction takes place and tetramethyllead in appreciable quantities is produced. Since the catalyst system is easy to handle and not subject to some of the severe conditions typically associated with the handling of alkyl aluminum complex catalyst and gaseous catalyst heretofore employed in the prior art, an advantage is readily appreciated utilizing these catalyst systems for the manufacture of tetramethyllead.

While the invention has been described with reference to certain specific embodiments, it is not intended that it .lereent TML yield (based on Na M ole of material per mole of alloy used Percent charged) by- Anthra- Methyl sodium Run N0. cene Diglymo Methanol chloride reacted (1.0. EDTA 9 1 0. 030 0. 0 0. 075 7. 35 14. 6 3. 3 2. 1 2 0. 030 0. 090 0. 0 7. 2O 1. 5 1. 5 1. 0 3 O. 030 O. O. 085 7. 20 100 48. 7 52. 6 4 0. 0 0. 085 0. 080 7. 65 54. 6 29. 7 32. 2 5 0. 030 0. 065 0. 6. G0 G5. 0 32. 6 36. 3 6. O. 055 0. 090 0. 085 6. 95 66. 8 42. 9 45. 3

1 Analysis by gas chromatograph. I 2 Analysis by cthylenediaminetetraaeetic acid titration EXAMPLE III A further set of runs were made utilizing 0.2 mole of /1" to 40 mesh flakes of sodium-lead alloy and various quantities of methyl chloride. In these runs the catalyst be so limited except insofar as appears in the accompanying claims.

What is claimed is:

1. A method of preparing tetramethyllead comprising contacting methyl halide and sodium lead alloy in the system anthracene, methanol and diglyme was utilized 75 presence of sutiicient catalyst to cause them to react and form tetramethyllead, the catalyst comprising 70 to 90 percent by weight diglyme and 30 to percent by weight methanol.

2. A method of preparing tetramethyllead comprising contacting methyl halide and sodium lead alloy in the presence of sutficient catalyst to cause them to react and form tetramethyllead, the catalyst comprising 58 to 79.9 percent by weight diglyme, 14 to 20 percent by weight methanol and 0.1 to 28 percent by weight anthracene.

3. A method of preparing tetramethyllead comprising reacting methyl halide and sodium-lead alloy in the presence of a methanol-diglyme catalyst composition, the diglyme being present in an amount of from 0.01 mole to 0.2 mole per mole of sodium-lead alloy and the methanol being present in an amount of from 0.01 to 0.2 mole per mole of sodium-lead alloy.

4. A method of preparing tetramethyllead comprising reacting methyl halide and sodium-lead alloy in the presence of a methanol-diglyme-anthracene catalyst composition, the diglyme being present in an amount of from 0.01 mole to 0.2 mole per mole of sodium-lead alloy, the methanol being present in amount amount of from 0.01 mole to 0.2 mole per mole of sodium lead alloy and the anthracene being present in an amount of from 0.001 to 0.1 mole per mole of sodium-lead alloy.

5. The method of claim 1 wherein the reaction is conducted at a temperature of about -20 C. to 150 C.

6. The method of claim 2 wherein the reaction is conducted at temperature of about 20 C. to 150 C. 7. The method of claim 3 wherein the reaction is conducted at temperature of about 20 C. to 150 C.

References Cited UNITED STATES PATENTS 1,645,390 10/1927 Monroe 260437 R 1,661,809 3/1928 Monroe 260437 R 1,661,810 3/1928 Monroe 260437 R 1,717,961 6/1929 Daudt et a1. 260437 R 3,192,240 6/1965 Kobetz et al 260437 R 3,226,409 12/1965 Beaird et a1. 260437 R 3,281,442 10/1966 Pedrotti et al. 260437 R 3,359,291 12/1967 Braithwaite et a1. 260437 R 3,401,188 9/1968 Sandy 260437 R 3,401,189 9/1968 Sandy et al 260437 R JAMES E. POER, Primary Examiner H. M. S. SNEED, Assistant Examiner US. Cl. X.R. 252426 

